1. Field of the Invention
The invention relates to a process for preserving raw coffee extract.
Raw coffee extract is an important and immediate factor in the manufacture of special coffee formulations.
2. Description of the Related Art
EP-B-0,008,398 has disclosed a process for decaffeinating coffee, wherein caffeine is extracted from the raw coffee by means of an aqueous caffeine-free raw coffee extract solution (equilibrium solution). The equilibrium solution (raw coffee extract) enriched in caffeine is passed through a preloaded activated carbon adsorber, the caffeine being adsorbed selectively. It is then only necessary to dry the beans thus decaffeinated.
The cafffeine-free raw coffee bean extract used in EP-B-0,008,398 contains coffee constituents--apart from caffeine --in such concentrations that nothing other than caffeine is dissolved out of the coffee beans, since the concentrations in an aqueous solution are in equilibrium with the concentrations in the coffee bean.
In the text which follows, raw coffee extract and equilibrium solution are to be understood as caffeine-containing raw coffee extract and decaffeinated raw coffee extract respectively.
In the said continuous decaffeination process according to EP-B-0,008,398, the raw coffee extract is used always at about 80.degree. C. in the process. The temperature of about 80.degree. C. is necessary for two reasons:
1. it allows a considerably accelerated diffusion of caffeine, and
2. it prevents microbiological spoilage of the solution.
At temperatures below about 60.degree. C., rapid growth of organisms can occur in the solution (fermentation). The constituents of the solution are altered, leading to disadvantageous impairment of the taste of the coffee treated with the solution. In this case, the spoiled equilibrium solution must be discarded an da new solution must be prepared. In addition to a considerable loss of time, the loss in value due to the discarded extract solution represents a considerable cost factor.
In the event of prolonged interruptions in operation, the equilibrium solution must therefore be held at a constant temperature of about 80.degree. C. in special tanks. Evaporation losses of water must be continuously made up. This type of storage is very energy-consuming and prone to faults. Fluctuations in the temperature and concentration of the extract can cause adverse changes in the aroma of the raw coffee extract and of the coffee treated with the extract.